PEOFESSOR OWEN ON THE SPECIES OF PHASCOLOMTS. 351 



In Ph. platyrhinus (PI. LIII. fig. 6) and Ph. vombatus the two divisions of the supra- 

 tympanic cell are more equal, and the ' gomphosis ' of the squamosal with the tympanic 

 is less marked. The malar part (PI. L. fig. 1, 26) of the zygoma defines the orbit pos- 

 teriorly by an angular process in both the bare-nosed Wombats ; it is not developed 

 in the hairy-nosed species, where the hind boundary of the orbit is indicated by the 

 postfrontal process (PI. LIII. fig. 1, 12) which is not present or is rudimental in the 

 others. 



The numerous irregular venous foramina of the squamosal (Pis. L., LI. 27) are 

 notable iu all the species of Wombat. 



The superior maxillary sends outward and backward a process (PI. LII. fig. 1, 21*) 

 which contributes to and strengthens the anterior pier (ib. 26) of the zygomatic arch ; 

 it projects above the alveolus of the third and fourth molar teeth, at a greater height 

 above the molars in Ph. latifrons (PI. LVI. fig. 5, 2i») than in Ph. platyrhinus (ib. fig. 4) 

 or in Ph. vombatus. In a skull of the larger bare-nosed species, with an upper molar 

 series 2 inches 2 lines in extent, the process rises 7 lines above the outlet of the third 

 molar alveolus. In the skull of a Ph. latifrons with a molar series 1 inch 11 lines in 

 extent, the process rises 10 lines above that outlet. In other words, the outer alveolar 

 plate of the maxillary is deeper, below the zygoma, in the hairy-nosed than in the bare- 

 nosed Wombats : it is, also, more nearly vertical, less inclined mesiad as it descends to 

 the outlets of the sockets. 



In my first memoir I state that " PJiascolomys resembles Phascolarctiis and Hypsi- 

 prymnus in having the posterior palatal openings large and situated entirely in the 

 palatal bones," and that " posterior and external to these are two small perforations " '. 

 In the other two species (Phascolomys j^latyrJiinus and Ph. latifrons), determined since 

 the date of that remark, which was made on the skull of Ph. vombatus, the generic cha- 

 racters of the postpalatal apertui'es are repeated. In the skull of Ph. vombatus, figured 

 in PI. Ixxi. fig. 6, of the 2nd volume of the ' Zoological Transactions,' these apertures 

 are oval, the base, which is behind, being rounded ; but the small end of the oval is so 

 nearly pointed as to suggest the term ' triangular.' In two skulls of full-grown Tasma- 

 nian Wombats, since compared, these foramina present the same shape and proportions 

 (PI. LII. fig. 4, b) ; in two smaller and younger skulls of Ph. vombatus they are rela- 

 tively smaller, and are rather elliptical than oval. In two skulls of Ph. platyrhinus, 

 in the British Museum, the postpalatal apertures are longitudinally elliptical or oblong 

 in one (ib. fig. 1, b) and are triangular in the other: in both, the apertures extend more 

 forward and come near to the transverse parallel of the middle of the hindmost 

 socket (ib. ib. ms). In three skulls oi Ph. latifrons the postpalatal foramina (PI. LII. 

 fig. 5 ; PI. LIII. fig. 1, b) are relatively larger, especially longer, than in either the 

 Tasmanian or platyrhine Wombat, and are rounded anteriorly but less broad there 

 than behind : they advance nearer to the fore part of the last molar alveolus, or reach 

 ' " On the Osteolog)- of the Marsupialia,'' Trans. Zool. Soc. vol. ii. p. 389. 



